The use of a phosphor to convert the wavelength in a light-emitting diode (LED) is widely known in the field of LED device production (Patent Literature 1). In fact, much academic attention has been focused on a light-resistant silicone resin as a material for coating an LED device for encapsulation and protection (Patent Literature 2).
Generally, as for a white LED, a method for coating an LED chip with a silicone resin and an epoxy resin in which a phosphor is dispersed converts a blue light into a pseudo white light by dispersing the phosphor near the chip. However, a phosphor that is ununiformly dispersed or deviated in a resin layer can readily cause discoloration. Thus, in order to provide a phosphor with a uniform white light, the phosphor is required to uniformly be dispersed in a coated resin layer. Under the circumstances, a method for molding and curing a phosphor-containing silicone resin composition, processing it in the form of a film and gluing with an adhesive has attracted much technical attention. This method can fail to provide sufficient performance such as LED luminance due to light leakage and loss of light in an adhesive layer. In addition, a process for laminating a thermosetting silicone resin on an LED device essentially requires complicated production processes (Patent Literature 3).
A method for using a sheet-formed encapsulating material is associated with a difficulty of an LED having a wire pad to be bored on a bonding pad and to be laminated only in the form of a chip.
In LED device production, a resin layer for coating an LED device is required to have a high heat resistance and a high ultraviolet resistance. In a conventional LED production apparatus, it is advantageous to form a resin layer in which a phosphor is uniformly dispersed.